[ViewVC] Diff of: cvs/AnyEvent-Fork/Fork.pm

Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.29 by root, Sat Apr 6 09:15:49 2013 UTC vs.
Revision 1.66 by root, Sat Jun 20 13:24:54 2015 UTC

…		…
27		27
28	Special care has been taken to make this module useful from other modules,	28	Special care has been taken to make this module useful from other modules,
29	while still supporting specialised environments such as L<App::Staticperl>	29	while still supporting specialised environments such as L<App::Staticperl>
30	or L<PAR::Packer>.	30	or L<PAR::Packer>.
31		31
32	=head1 WHAT THIS MODULE IS NOT	32	=head2 WHAT THIS MODULE IS NOT
33		33
34	This module only creates processes and lets you pass file handles and	34	This module only creates processes and lets you pass file handles and
35	strings to it, and run perl code. It does not implement any kind of RPC -	35	strings to it, and run perl code. It does not implement any kind of RPC -
36	there is no back channel from the process back to you, and there is no RPC	36	there is no back channel from the process back to you, and there is no RPC
37	or message passing going on.	37	or message passing going on.
38		38
39	If you need some form of RPC, you can either implement it yourself	39	If you need some form of RPC, you could use the L<AnyEvent::Fork::RPC>
40	in whatever way you like, use some message-passing module such	40	companion module, which adds simple RPC/job queueing to a process created
41	as L<AnyEvent::MP>, some pipe such as L<AnyEvent::ZeroMQ>, use	41	by this module.
42	L<AnyEvent::Handle> on both sides to send e.g. JSON or Storable messages,
43	and so on.
44		42
		43	And if you need some automatic process pool management on top of
		44	L<AnyEvent::Fork::RPC>, you can look at the L<AnyEvent::Fork::Pool>
		45	companion module.
		46
		47	Or you can implement it yourself in whatever way you like: use some
		48	message-passing module such as L<AnyEvent::MP>, some pipe such as
		49	L<AnyEvent::ZeroMQ>, use L<AnyEvent::Handle> on both sides to send
		50	e.g. JSON or Storable messages, and so on.
		51
		52	=head2 COMPARISON TO OTHER MODULES
		53
		54	There is an abundance of modules on CPAN that do "something fork", such as
		55	L<Parallel::ForkManager>, L<AnyEvent::ForkManager>, L<AnyEvent::Worker>
		56	or L<AnyEvent::Subprocess>. There are modules that implement their own
		57	process management, such as L<AnyEvent::DBI>.
		58
		59	The problems that all these modules try to solve are real, however, none
		60	of them (from what I have seen) tackle the very real problems of unwanted
		61	memory sharing, efficiency or not being able to use event processing, GUI
		62	toolkits or similar modules in the processes they create.
		63
		64	This module doesn't try to replace any of them - instead it tries to solve
		65	the problem of creating processes with a minimum of fuss and overhead (and
		66	also luxury). Ideally, most of these would use AnyEvent::Fork internally,
		67	except they were written before AnyEvent:Fork was available, so obviously
		68	had to roll their own.
		69
45	=head1 PROBLEM STATEMENT	70	=head2 PROBLEM STATEMENT
46		71
47	There are two traditional ways to implement parallel processing on UNIX	72	There are two traditional ways to implement parallel processing on UNIX
48	like operating systems - fork and process, and fork+exec and process. They	73	like operating systems - fork and process, and fork+exec and process. They
49	have different advantages and disadvantages that I describe below,	74	have different advantages and disadvantages that I describe below,
50	together with how this module tries to mitigate the disadvantages.	75	together with how this module tries to mitigate the disadvantages.
…		…
64		89
65	=item Forking usually creates a copy-on-write copy of the parent	90	=item Forking usually creates a copy-on-write copy of the parent
66	process.	91	process.
67		92
68	For example, modules or data files that are loaded will not use additional	93	For example, modules or data files that are loaded will not use additional
69	memory after a fork. When exec'ing a new process, modules and data files	94	memory after a fork. Exec'ing a new process, in contrast, means modules
70	might need to be loaded again, at extra CPU and memory cost. But when	95	and data files might need to be loaded again, at extra CPU and memory
71	forking, literally all data structures are copied - if the program frees	96	cost.
		97
		98	But when forking, you still create a copy of your data structures - if
72	them and replaces them by new data, the child processes will retain the	99	the program frees them and replaces them by new data, the child processes
73	old version even if it isn't used, which can suddenly and unexpectedly	100	will retain the old version even if it isn't used, which can suddenly and
74	increase memory usage when freeing memory.	101	unexpectedly increase memory usage when freeing memory.
75		102
		103	For example, L<Gtk2::CV> is an image viewer optimised for large
		104	directories (millions of pictures). It also forks subprocesses for
		105	thumbnail generation, which inherit the data structure that stores all
		106	file information. If the user changes the directory, it gets freed in
		107	the main process, leaving a copy in the thumbnailer processes. This can
		108	lead to many times the memory usage that would actually be required. The
		109	solution is to fork early (and being unable to dynamically generate more
		110	subprocesses or do this from a module)... or to use L<AnyEvent:Fork>.
		111
76	The trade-off is between more sharing with fork (which can be good or	112	There is a trade-off between more sharing with fork (which can be good or
77	bad), and no sharing with exec.	113	bad), and no sharing with exec.
78		114
79	This module allows the main program to do a controlled fork, and allows	115	This module allows the main program to do a controlled fork, and allows
80	modules to exec processes safely at any time. When creating a custom	116	modules to exec processes safely at any time. When creating a custom
81	process pool you can take advantage of data sharing via fork without	117	process pool you can take advantage of data sharing via fork without
…		…
86	shared and what isn't, at all times.	122	shared and what isn't, at all times.
87		123
88	=item Exec'ing a new perl process might be difficult.	124	=item Exec'ing a new perl process might be difficult.
89		125
90	For example, it is not easy to find the correct path to the perl	126	For example, it is not easy to find the correct path to the perl
91	interpreter - C<$^X> might not be a perl interpreter at all.	127	interpreter - C<$^X> might not be a perl interpreter at all. Worse, there
		128	might not even be a perl binary installed on the system.
92		129
93	This module tries hard to identify the correct path to the perl	130	This module tries hard to identify the correct path to the perl
94	interpreter. With a cooperative main program, exec'ing the interpreter	131	interpreter. With a cooperative main program, exec'ing the interpreter
95	might not even be necessary, but even without help from the main program,	132	might not even be necessary, but even without help from the main program,
96	it will still work when used from a module.	133	it will still work when used from a module.
…		…
102	and modules are no longer loadable because they refer to a different	139	and modules are no longer loadable because they refer to a different
103	perl version, or parts of a distribution are newer than the ones already	140	perl version, or parts of a distribution are newer than the ones already
104	loaded.	141	loaded.
105		142
106	This module supports creating pre-initialised perl processes to be used as	143	This module supports creating pre-initialised perl processes to be used as
107	a template for new processes.	144	a template for new processes at a later time, e.g. for use in a process
		145	pool.
108		146
109	=item Forking might be impossible when a program is running.	147	=item Forking might be impossible when a program is running.
110		148
111	For example, POSIX makes it almost impossible to fork from a	149	For example, POSIX makes it almost impossible to fork from a
112	multi-threaded program while doing anything useful in the child - in	150	multi-threaded program while doing anything useful in the child - in
113	fact, if your perl program uses POSIX threads (even indirectly via	151	fact, if your perl program uses POSIX threads (even indirectly via
114	e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level	152	e.g. L<IO::AIO> or L<threads>), you cannot call fork on the perl level
115	anymore without risking corruption issues on a number of operating	153	anymore without risking memory corruption or worse on a number of
116	systems.	154	operating systems.
117		155
118	This module can safely fork helper processes at any time, by calling	156	This module can safely fork helper processes at any time, by calling
119	fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>).	157	fork+exec in C, in a POSIX-compatible way (via L<Proc::FastSpawn>).
120		158
121	=item Parallel processing with fork might be inconvenient or difficult	159	=item Parallel processing with fork might be inconvenient or difficult
…		…
140		178
141	=back	179	=back
142		180
143	=head1 EXAMPLES	181	=head1 EXAMPLES
144		182
		183	This is where the wall of text ends and code speaks.
		184
145	=head2 Create a single new process, tell it to run your worker function.	185	=head2 Create a single new process, tell it to run your worker function.
146		186
147	AnyEvent::Fork	187	AnyEvent::Fork
148	->new	188	->new
149	->require ("MyModule")	189	->require ("MyModule")
…		…
152		192
153	# now $master_filehandle is connected to the	193	# now $master_filehandle is connected to the
154	# $slave_filehandle in the new process.	194	# $slave_filehandle in the new process.
155	});	195	});
156		196
157	# MyModule::worker might look like this	197	C<MyModule> might look like this:
		198
		199	package MyModule;
		200
158	sub MyModule::worker {	201	sub worker {
159	my ($slave_filehandle) = @_;	202	my ($slave_filehandle) = @_;
160		203
161	# now $slave_filehandle is connected to the $master_filehandle	204	# now $slave_filehandle is connected to the $master_filehandle
162	# in the original prorcess. have fun!	205	# in the original process. have fun!
163	}	206	}
164		207
165	=head2 Create a pool of server processes all accepting on the same socket.	208	=head2 Create a pool of server processes all accepting on the same socket.
166		209
167	# create listener socket	210	# create listener socket
…		…
182	}	225	}
183		226
184	# now do other things - maybe use the filehandle provided by run	227	# now do other things - maybe use the filehandle provided by run
185	# to wait for the processes to die. or whatever.	228	# to wait for the processes to die. or whatever.
186		229
187	# My::Server::run might look like this	230	C<My::Server> might look like this:
188	sub My::Server::run {	231
		232	package My::Server;
		233
		234	sub run {
189	my ($slave, $listener, $id) = @_;	235	my ($slave, $listener, $id) = @_;
190		236
191	close $slave; # we do not use the socket, so close it to save resources	237	close $slave; # we do not use the socket, so close it to save resources
192		238
193	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,	239	# we could go ballistic and use e.g. AnyEvent here, or IO::AIO,
…		…
197	}	243	}
198	}	244	}
199		245
200	=head2 use AnyEvent::Fork as a faster fork+exec	246	=head2 use AnyEvent::Fork as a faster fork+exec
201		247
202	This runs /bin/echo hi, with stdout redirected to /tmp/log and stderr to	248	This runs C</bin/echo hi>, with standard output redirected to F</tmp/log>
203	the communications socket. It is usually faster than fork+exec, but still	249	and standard error redirected to the communications socket. It is usually
204	let's you prepare the environment.	250	faster than fork+exec, but still lets you prepare the environment.
205		251
206	open my $output, ">/tmp/log" or die "$!";	252	open my $output, ">/tmp/log" or die "$!";
207		253
208	AnyEvent::Fork	254	AnyEvent::Fork
209	->new	255	->new
210	->eval ('	256	->eval ('
		257	# compile a helper function for later use
211	sub run {	258	sub run {
212	my ($fh, $output, @cmd) = @_;	259	my ($fh, $output, @cmd) = @_;
213		260
214	# perl will clear close-on-exec on STDOUT/STDERR	261	# perl will clear close-on-exec on STDOUT/STDERR
215	open STDOUT, ">&", $output or die;	262	open STDOUT, ">&", $output or die;
…		…
222	->send_arg ("/bin/echo", "hi")	269	->send_arg ("/bin/echo", "hi")
223	->run ("run", my $cv = AE::cv);	270	->run ("run", my $cv = AE::cv);
224		271
225	my $stderr = $cv->recv;	272	my $stderr = $cv->recv;
226		273
		274	=head2 For stingy users: put the worker code into a C<DATA> section.
		275
		276	When you want to be stingy with files, you can put your code into the
		277	C<DATA> section of your module (or program):
		278
		279	use AnyEvent::Fork;
		280
		281	AnyEvent::Fork
		282	->new
		283	->eval (do { local $/; <DATA> })
		284	->run ("doit", sub { ... });
		285
		286	__DATA__
		287
		288	sub doit {
		289	... do something!
		290	}
		291
		292	=head2 For stingy standalone programs: do not rely on external files at
		293	all.
		294
		295	For single-file scripts it can be inconvenient to rely on external
		296	files - even when using a C<DATA> section, you still need to C<exec> an
		297	external perl interpreter, which might not be available when using
		298	L<App::Staticperl>, L<Urlader> or L<PAR::Packer> for example.
		299
		300	Two modules help here - L<AnyEvent::Fork::Early> forks a template process
		301	for all further calls to C<new_exec>, and L<AnyEvent::Fork::Template>
		302	forks the main program as a template process.
		303
		304	Here is how your main program should look like:
		305
		306	#! perl
		307
		308	# optional, as the very first thing.
		309	# in case modules want to create their own processes.
		310	use AnyEvent::Fork::Early;
		311
		312	# next, load all modules you need in your template process
		313	use Example::My::Module
		314	use Example::Whatever;
		315
		316	# next, put your run function definition and anything else you
		317	# need, but do not use code outside of BEGIN blocks.
		318	sub worker_run {
		319	my ($fh, @args) = @_;
		320	...
		321	}
		322
		323	# now preserve everything so far as AnyEvent::Fork object
		324	# in $TEMPLATE.
		325	use AnyEvent::Fork::Template;
		326
		327	# do not put code outside of BEGIN blocks until here
		328
		329	# now use the $TEMPLATE process in any way you like
		330
		331	# for example: create 10 worker processes
		332	my @worker;
		333	my $cv = AE::cv;
		334	for (1..10) {
		335	$cv->begin;
		336	$TEMPLATE->fork->send_arg ($_)->run ("worker_run", sub {
		337	push @worker, shift;
		338	$cv->end;
		339	});
		340	}
		341	$cv->recv;
		342
227	=head1 CONCEPTS	343	=head1 CONCEPTS
228		344
229	This module can create new processes either by executing a new perl	345	This module can create new processes either by executing a new perl
230	process, or by forking from an existing "template" process.	346	process, or by forking from an existing "template" process.
		347
		348	All these processes are called "child processes" (whether they are direct
		349	children or not), while the process that manages them is called the
		350	"parent process".
231		351
232	Each such process comes with its own file handle that can be used to	352	Each such process comes with its own file handle that can be used to
233	communicate with it (it's actually a socket - one end in the new process,	353	communicate with it (it's actually a socket - one end in the new process,
234	one end in the main process), and among the things you can do in it are	354	one end in the main process), and among the things you can do in it are
235	load modules, fork new processes, send file handles to it, and execute	355	load modules, fork new processes, send file handles to it, and execute
…		…
345	use AnyEvent;	465	use AnyEvent;
346	use AnyEvent::Util ();	466	use AnyEvent::Util ();
347		467
348	use IO::FDPass;	468	use IO::FDPass;
349		469
350	our $VERSION = 0.5;	470	our $VERSION = 1.2;
351
352	our $PERL; # the path to the perl interpreter, deduces with various forms of magic
353
354	=over 4
355
356	=back
357
358	=cut
359		471
360	# the early fork template process	472	# the early fork template process
361	our $EARLY;	473	our $EARLY;
362		474
363	# the empty template process	475	# the empty template process
364	our $TEMPLATE;	476	our $TEMPLATE;
		477
		478	sub QUEUE() { 0 }
		479	sub FH() { 1 }
		480	sub WW() { 2 }
		481	sub PID() { 3 }
		482	sub CB() { 4 }
		483
		484	sub _new {
		485	my ($self, $fh, $pid) = @_;
		486
		487	AnyEvent::Util::fh_nonblocking $fh, 1;
		488
		489	$self = bless [
		490	[], # write queue - strings or fd's
		491	$fh,
		492	undef, # AE watcher
		493	$pid,
		494	], $self;
		495
		496	$self
		497	}
365		498
366	sub _cmd {	499	sub _cmd {
367	my $self = shift;	500	my $self = shift;
368		501
369	# ideally, we would want to use "a (w/a)*" as format string, but perl	502	# ideally, we would want to use "a (w/a)*" as format string, but perl
370	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack	503	# versions from at least 5.8.9 to 5.16.3 are all buggy and can't unpack
371	# it.	504	# it.
372	push @{ $self->[2] }, pack "a L/a*", $_[0], $_[1];	505	push @{ $self->[QUEUE] }, pack "a L/a*", $_[0], $_[1];
373		506
374	$self->[3] \|\|= AE::io $self->[1], 1, sub {	507	$self->[WW] \|\|= AE::io $self->[FH], 1, sub {
375	do {	508	do {
376	# send the next "thing" in the queue - either a reference to an fh,	509	# send the next "thing" in the queue - either a reference to an fh,
377	# or a plain string.	510	# or a plain string.
378		511
379	if (ref $self->[2][0]) {	512	if (ref $self->[QUEUE][0]) {
380	# send fh	513	# send fh
381	unless (IO::FDPass::send fileno $self->[1], fileno ${ $self->[2][0] }) {	514	unless (IO::FDPass::send fileno $self->[FH], fileno ${ $self->[QUEUE][0] }) {
382	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	515	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
383	undef $self->[3];	516	undef $self->[WW];
384	die "AnyEvent::Fork: file descriptor send failure: $!";	517	die "AnyEvent::Fork: file descriptor send failure: $!";
385	}	518	}
386		519
387	shift @{ $self->[2] };	520	shift @{ $self->[QUEUE] };
388		521
389	} else {	522	} else {
390	# send string	523	# send string
391	my $len = syswrite $self->[1], $self->[2][0];	524	my $len = syswrite $self->[FH], $self->[QUEUE][0];
392		525
393	unless ($len) {	526	unless ($len) {
394	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;	527	return if $! == Errno::EAGAIN \|\| $! == Errno::EWOULDBLOCK;
395	undef $self->[3];	528	undef $self->[WW];
396	die "AnyEvent::Fork: command write failure: $!";	529	die "AnyEvent::Fork: command write failure: $!";
397	}	530	}
398		531
399	substr $self->[2][0], 0, $len, "";	532	substr $self->[QUEUE][0], 0, $len, "";
400	shift @{ $self->[2] } unless length $self->[2][0];	533	shift @{ $self->[QUEUE] } unless length $self->[QUEUE][0];
401	}	534	}
402	} while @{ $self->[2] };	535	} while @{ $self->[QUEUE] };
403		536
404	# everything written	537	# everything written
405	undef $self->[3];	538	undef $self->[WW];
406		539
407	# invoke run callback, if any	540	# invoke run callback, if any
408	$self->[4]->($self->[1]) if $self->[4];	541	if ($self->[CB]) {
		542	$self->[CB]->($self->[FH]);
		543	@$self = ();
		544	}
409	};	545	};
410		546
411	() # make sure we don't leak the watcher	547	() # make sure we don't leak the watcher
412	}
413
414	sub _new {
415	my ($self, $fh, $pid) = @_;
416
417	AnyEvent::Util::fh_nonblocking $fh, 1;
418
419	$self = bless [
420	$pid,
421	$fh,
422	[], # write queue - strings or fd's
423	undef, # AE watcher
424	], $self;
425
426	$self
427	}	548	}
428		549
429	# fork template from current process, used by AnyEvent::Fork::Early/Template	550	# fork template from current process, used by AnyEvent::Fork::Early/Template
430	sub _new_fork {	551	sub _new_fork {
431	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	552	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
436	if ($pid eq 0) {	557	if ($pid eq 0) {
437	require AnyEvent::Fork::Serve;	558	require AnyEvent::Fork::Serve;
438	$AnyEvent::Fork::Serve::OWNER = $parent;	559	$AnyEvent::Fork::Serve::OWNER = $parent;
439	close $fh;	560	close $fh;
440	$0 = "$_[1] of $parent";	561	$0 = "$_[1] of $parent";
441	$SIG{CHLD} = 'IGNORE';
442	AnyEvent::Fork::Serve::serve ($slave);	562	AnyEvent::Fork::Serve::serve ($slave);
443	exit 0;	563	exit 0;
444	} elsif (!$pid) {	564	} elsif (!$pid) {
445	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";	565	die "AnyEvent::Fork::Early/Template: unable to fork template process: $!";
446	}	566	}
…		…
500		620
501	You should use C<new> whenever possible, except when having a template	621	You should use C<new> whenever possible, except when having a template
502	process around is unacceptable.	622	process around is unacceptable.
503		623
504	The path to the perl interpreter is divined using various methods - first	624	The path to the perl interpreter is divined using various methods - first
505	C<$^X> is investigated to see if the path ends with something that sounds	625	C<$^X> is investigated to see if the path ends with something that looks
506	as if it were the perl interpreter. Failing this, the module falls back to	626	as if it were the perl interpreter. Failing this, the module falls back to
507	using C<$Config::Config{perlpath}>.	627	using C<$Config::Config{perlpath}>.
508		628
		629	The path to perl can also be overriden by setting the global variable
		630	C<$AnyEvent::Fork::PERL> - it's value will be used for all subsequent
		631	invocations.
		632
509	=cut	633	=cut
		634
		635	our $PERL;
510		636
511	sub new_exec {	637	sub new_exec {
512	my ($self) = @_;	638	my ($self) = @_;
513		639
514	return $EARLY->fork	640	return $EARLY->fork
515	if $EARLY;	641	if $EARLY;
516		642
		643	unless (defined $PERL) {
517	# first find path of perl	644	# first find path of perl
518	my $perl = $;	645	my $perl = $^X;
519		646
520	# first we try $^X, but the path must be absolute (always on win32), and end in sth.	647	# first we try $^X, but the path must be absolute (always on win32), and end in sth.
521	# that looks like perl. this obviously only works for posix and win32	648	# that looks like perl. this obviously only works for posix and win32
522	unless (	649	unless (
523	($^O eq "MSWin32" \|\| $perl =~ m%^/%)	650	($^O eq "MSWin32" \|\| $perl =~ m%^/%)
524	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i	651	&& $perl =~ m%[/\\]perl(?:[0-9]+(\.[0-9]+)+)?(\.exe)?$%i
525	) {	652	) {
526	# if it doesn't look perlish enough, try Config	653	# if it doesn't look perlish enough, try Config
527	require Config;	654	require Config;
528	$perl = $Config::Config{perlpath};	655	$perl = $Config::Config{perlpath};
529	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;	656	$perl =~ s/(?:\Q$Config::Config{_exe}\E)?$/$Config::Config{_exe}/;
		657	}
		658
		659	$PERL = $perl;
530	}	660	}
531		661
532	require Proc::FastSpawn;	662	require Proc::FastSpawn;
533		663
534	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;	664	my ($fh, $slave) = AnyEvent::Util::portable_socketpair;
…		…
542	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;	672	#local $ENV{PERL5LIB} = join ":", grep !ref, @INC;
543	my %env = %ENV;	673	my %env = %ENV;
544	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;	674	$env{PERL5LIB} = join +($^O eq "MSWin32" ? ";" : ":"), grep !ref, @INC;
545		675
546	my $pid = Proc::FastSpawn::spawn (	676	my $pid = Proc::FastSpawn::spawn (
547	$perl,	677	$PERL,
548	["perl", "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],	678	[$PERL, "-MAnyEvent::Fork::Serve", "-e", "AnyEvent::Fork::Serve::me", fileno $slave, $$],
549	[map "$_=$env{$_}", keys %env],	679	[map "$_=$env{$_}", keys %env],
550	) or die "unable to spawn AnyEvent::Fork server: $!";	680	) or die "unable to spawn AnyEvent::Fork server: $!";
551		681
552	$self->_new ($fh, $pid)	682	$self->_new ($fh, $pid)
553	}	683	}
554		684
555	=item $pid = $proc->pid	685	=item $pid = $proc->pid
556		686
557	Returns the process id of the process I<iff it is a direct child of the	687	Returns the process id of the process I<iff it is a direct child of the
558	process> running AnyEvent::Fork, and C<undef> otherwise.	688	process running AnyEvent::Fork>, and C<undef> otherwise. As a general
		689	rule (that you cannot rely upon), processes created via C<new_exec>,
		690	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template> are direct
		691	children, while all other processes are not.
559		692
560	Normally, only processes created via C<< AnyEvent::Fork->new_exec >> and	693	Or in other words, you do not normally have to take care of zombies for
561	L<AnyEvent::Fork::Template> are direct children, and you are responsible	694	processes created via C<new>, but when in doubt, or zombies are a problem,
562	to clean up their zombies when they die.	695	you need to check whether a process is a diretc child by calling this
563		696	method, and possibly creating a child watcher or reap it manually.
564	All other processes are not direct children, and will be cleaned up by
565	AnyEvent::Fork.
566		697
567	=cut	698	=cut
568		699
569	sub pid {	700	sub pid {
570	$_[0][0]	701	$_[0][PID]
571	}	702	}
572		703
573	=item $proc = $proc->eval ($perlcode, @args)	704	=item $proc = $proc->eval ($perlcode, @args)
574		705
575	Evaluates the given C<$perlcode> as ... perl code, while setting C<@_> to	706	Evaluates the given C<$perlcode> as ... Perl code, while setting C<@_> to
576	the strings specified by C<@args>, in the "main" package.	707	the strings specified by C<@args>, in the "main" package.
577		708
578	This call is meant to do any custom initialisation that might be required	709	This call is meant to do any custom initialisation that might be required
579	(for example, the C<require> method uses it). It's not supposed to be used	710	(for example, the C<require> method uses it). It's not supposed to be used
580	to completely take over the process, use C<run> for that.	711	to completely take over the process, use C<run> for that.
581		712
582	The code will usually be executed after this call returns, and there is no	713	The code will usually be executed after this call returns, and there is no
583	way to pass anything back to the calling process. Any evaluation errors	714	way to pass anything back to the calling process. Any evaluation errors
584	will be reported to stderr and cause the process to exit.	715	will be reported to stderr and cause the process to exit.
585		716
586	If you want to execute some code to take over the process (see the	717	If you want to execute some code (that isn't in a module) to take over the
587	"fork+exec" example in the SYNOPSIS), you should compile a function via	718	process, you should compile a function via C<eval> first, and then call
588	C<eval> first, and then call it via C<run>. This also gives you access to	719	it via C<run>. This also gives you access to any arguments passed via the
589	any arguments passed via the C<send_xxx> methods, such as file handles.	720	C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as
		721	a faster fork+exec> example to see it in action.
590		722
591	Returns the process object for easy chaining of method calls.	723	Returns the process object for easy chaining of method calls.
		724
		725	It's common to want to call an iniitalisation function with some
		726	arguments. Make sure you actually pass C<@_> to that function (for example
		727	by using C<&name> syntax), and do not just specify a function name:
		728
		729	$proc->eval ('&MyModule::init', $string1, $string2);
592		730
593	=cut	731	=cut
594		732
595	sub eval {	733	sub eval {
596	my ($self, $code, @args) = @_;	734	my ($self, $code, @args) = @_;
…		…
620	=item $proc = $proc->send_fh ($handle, ...)	758	=item $proc = $proc->send_fh ($handle, ...)
621		759
622	Send one or more file handles (I<not> file descriptors) to the process,	760	Send one or more file handles (I<not> file descriptors) to the process,
623	to prepare a call to C<run>.	761	to prepare a call to C<run>.
624		762
625	The process object keeps a reference to the handles until this is done,	763	The process object keeps a reference to the handles until they have
626	so you must not explicitly close the handles. This is most easily	764	been passed over to the process, so you must not explicitly close the
627	accomplished by simply not storing the file handles anywhere after passing	765	handles. This is most easily accomplished by simply not storing the file
628	them to this method.	766	handles anywhere after passing them to this method - when AnyEvent::Fork
		767	is finished using them, perl will automatically close them.
629		768
630	Returns the process object for easy chaining of method calls.	769	Returns the process object for easy chaining of method calls.
631		770
632	Example: pass a file handle to a process, and release it without	771	Example: pass a file handle to a process, and release it without
633	closing. It will be closed automatically when it is no longer used.	772	closing. It will be closed automatically when it is no longer used.
…		…
640	sub send_fh {	779	sub send_fh {
641	my ($self, @fh) = @_;	780	my ($self, @fh) = @_;
642		781
643	for my $fh (@fh) {	782	for my $fh (@fh) {
644	$self->_cmd ("h");	783	$self->_cmd ("h");
645	push @{ $self->[2] }, \$fh;	784	push @{ $self->[QUEUE] }, \$fh;
646	}	785	}
647		786
648	$self	787	$self
649	}	788	}
650		789
651	=item $proc = $proc->send_arg ($string, ...)	790	=item $proc = $proc->send_arg ($string, ...)
652		791
653	Send one or more argument strings to the process, to prepare a call to	792	Send one or more argument strings to the process, to prepare a call to
654	C<run>. The strings can be any octet string.	793	C<run>. The strings can be any octet strings.
655		794
656	The protocol is optimised to pass a moderate number of relatively short	795	The protocol is optimised to pass a moderate number of relatively short
657	strings - while you can pass up to 4GB of data in one go, this is more	796	strings - while you can pass up to 4GB of data in one go, this is more
658	meant to pass some ID information or other startup info, not big chunks of	797	meant to pass some ID information or other startup info, not big chunks of
659	data.	798	data.
…		…
675	Enter the function specified by the function name in C<$func> in the	814	Enter the function specified by the function name in C<$func> in the
676	process. The function is called with the communication socket as first	815	process. The function is called with the communication socket as first
677	argument, followed by all file handles and string arguments sent earlier	816	argument, followed by all file handles and string arguments sent earlier
678	via C<send_fh> and C<send_arg> methods, in the order they were called.	817	via C<send_fh> and C<send_arg> methods, in the order they were called.
679		818
		819	The process object becomes unusable on return from this function - any
		820	further method calls result in undefined behaviour.
		821
680	The function name should be fully qualified, but if it isn't, it will be	822	The function name should be fully qualified, but if it isn't, it will be
681	looked up in the main package.	823	looked up in the C<main> package.
682		824
683	If the called function returns, doesn't exist, or any error occurs, the	825	If the called function returns, doesn't exist, or any error occurs, the
684	process exits.	826	process exits.
685		827
686	Preparing the process is done in the background - when all commands have	828	Preparing the process is done in the background - when all commands have
687	been sent, the callback is invoked with the local communications socket	829	been sent, the callback is invoked with the local communications socket
688	as argument. At this point you can start using the socket in any way you	830	as argument. At this point you can start using the socket in any way you
689	like.	831	like.
690		832
691	The process object becomes unusable on return from this function - any
692	further method calls result in undefined behaviour.
693
694	If the communication socket isn't used, it should be closed on both sides,	833	If the communication socket isn't used, it should be closed on both sides,
695	to save on kernel memory.	834	to save on kernel memory.
696		835
697	The socket is non-blocking in the parent, and blocking in the newly	836	The socket is non-blocking in the parent, and blocking in the newly
698	created process. The close-on-exec flag is set in both.	837	created process. The close-on-exec flag is set in both.
699		838
700	Even if not used otherwise, the socket can be a good indicator for the	839	Even if not used otherwise, the socket can be a good indicator for the
701	existence of the process - if the other process exits, you get a readable	840	existence of the process - if the other process exits, you get a readable
702	event on it, because exiting the process closes the socket (if it didn't	841	event on it, because exiting the process closes the socket (if it didn't
703	create any children using fork).	842	create any children using fork).
		843
		844	=over 4
		845
		846	=item Compatibility to L<AnyEvent::Fork::Remote>
		847
		848	If you want to write code that works with both this module and
		849	L<AnyEvent::Fork::Remote>, you need to write your code so that it assumes
		850	there are two file handles for communications, which might not be unix
		851	domain sockets. The C<run> function should start like this:
		852
		853	sub run {
		854	my ($rfh, @args) = @_; # @args is your normal arguments
		855	my $wfh = fileno $rfh ? $rfh : *STDOUT;
		856
		857	# now use $rfh for reading and $wfh for writing
		858	}
		859
		860	This checks whether the passed file handle is, in fact, the process
		861	C<STDIN> handle. If it is, then the function was invoked visa
		862	L<AnyEvent::Fork::Remote>, so STDIN should be used for reading and
		863	C<STDOUT> should be used for writing.
		864
		865	In all other cases, the function was called via this module, and there is
		866	only one file handle that should be sued for reading and writing.
		867
		868	=back
704		869
705	Example: create a template for a process pool, pass a few strings, some	870	Example: create a template for a process pool, pass a few strings, some
706	file handles, then fork, pass one more string, and run some code.	871	file handles, then fork, pass one more string, and run some code.
707		872
708	my $pool = AnyEvent::Fork	873	my $pool = AnyEvent::Fork
…		…
736	=cut	901	=cut
737		902
738	sub run {	903	sub run {
739	my ($self, $func, $cb) = @_;	904	my ($self, $func, $cb) = @_;
740		905
741	$self->[4] = $cb;	906	$self->[CB] = $cb;
742	$self->_cmd (r => $func);	907	$self->_cmd (r => $func);
		908	}
		909
		910	=back
		911
		912	=head2 EXPERIMENTAL METHODS
		913
		914	These methods might go away completely or change behaviour, at any time.
		915
		916	=over 4
		917
		918	=item $proc->to_fh ($cb->($fh)) # EXPERIMENTAL, MIGHT BE REMOVED
		919
		920	Flushes all commands out to the process and then calls the callback with
		921	the communications socket.
		922
		923	The process object becomes unusable on return from this function - any
		924	further method calls result in undefined behaviour.
		925
		926	The point of this method is to give you a file handle that you can pass
		927	to another process. In that other process, you can call C<new_from_fh
		928	AnyEvent::Fork $fh> to create a new C<AnyEvent::Fork> object from it,
		929	thereby effectively passing a fork object to another process.
		930
		931	=cut
		932
		933	sub to_fh {
		934	my ($self, $cb) = @_;
		935
		936	$self->[CB] = $cb;
		937
		938	unless ($self->[WW]) {
		939	$self->[CB]->($self->[FH]);
		940	@$self = ();
		941	}
		942	}
		943
		944	=item new_from_fh AnyEvent::Fork $fh # EXPERIMENTAL, MIGHT BE REMOVED
		945
		946	Takes a file handle originally rceeived by the C<to_fh> method and creates
		947	a new C<AnyEvent:Fork> object. The child process itself will not change in
		948	any way, i.e. it will keep all the modifications done to it before calling
		949	C<to_fh>.
		950
		951	The new object is very much like the original object, except that the
		952	C<pid> method will return C<undef> even if the process is a direct child.
		953
		954	=cut
		955
		956	sub new_from_fh {
		957	my ($class, $fh) = @_;
		958
		959	$class->_new ($fh)
743	}	960	}
744		961
745	=back	962	=back
746		963
747	=head1 PERFORMANCE	964	=head1 PERFORMANCE
…		…
757		974
758	2079 new processes per second, using manual socketpair + fork	975	2079 new processes per second, using manual socketpair + fork
759		976
760	Then I did the same thing, but instead of calling fork, I called	977	Then I did the same thing, but instead of calling fork, I called
761	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the	978	AnyEvent::Fork->new->run ("CORE::exit") and then again waited for the
762	socket form the child to close on exit. This does the same thing as manual	979	socket from the child to close on exit. This does the same thing as manual
763	socket pair + fork, except that what is forked is the template process	980	socket pair + fork, except that what is forked is the template process
764	(2440kB), and the socket needs to be passed to the server at the other end	981	(2440kB), and the socket needs to be passed to the server at the other end
765	of the socket first.	982	of the socket first.
766		983
767	2307 new processes per second, using AnyEvent::Fork->new	984	2307 new processes per second, using AnyEvent::Fork->new
…		…
772	479 vfork+execs per second, using AnyEvent::Fork->new_exec	989	479 vfork+execs per second, using AnyEvent::Fork->new_exec
773		990
774	So how can C<< AnyEvent->new >> be faster than a standard fork, even	991	So how can C<< AnyEvent->new >> be faster than a standard fork, even
775	though it uses the same operations, but adds a lot of overhead?	992	though it uses the same operations, but adds a lot of overhead?
776		993
777	The difference is simply the process size: forking the 6MB process takes	994	The difference is simply the process size: forking the 5MB process takes
778	so much longer than forking the 2.5MB template process that the overhead	995	so much longer than forking the 2.5MB template process that the extra
779	introduced is canceled out.	996	overhead is canceled out.
780		997
781	If the benchmark process grows, the normal fork becomes even slower:	998	If the benchmark process grows, the normal fork becomes even slower:
782		999
783	1340 new processes, manual fork in a 20MB process	1000	1340 new processes, manual fork of a 20MB process
784	731 new processes, manual fork in a 200MB process	1001	731 new processes, manual fork of a 200MB process
785	235 new processes, manual fork in a 2000MB process	1002	235 new processes, manual fork of a 2000MB process
786		1003
787	What that means (to me) is that I can use this module without having a	1004	What that means (to me) is that I can use this module without having a bad
788	very bad conscience because of the extra overhead required to start new	1005	conscience because of the extra overhead required to start new processes.
789	processes.
790		1006
791	=head1 TYPICAL PROBLEMS	1007	=head1 TYPICAL PROBLEMS
792		1008
793	This section lists typical problems that remain. I hope by recognising	1009	This section lists typical problems that remain. I hope by recognising
794	them, most can be avoided.	1010	them, most can be avoided.
795		1011
796	=over 4	1012	=over 4
797		1013
798	=item "leaked" file descriptors for exec'ed processes	1014	=item leaked file descriptors for exec'ed processes
799		1015
800	POSIX systems inherit file descriptors by default when exec'ing a new	1016	POSIX systems inherit file descriptors by default when exec'ing a new
801	process. While perl itself laudably sets the close-on-exec flags on new	1017	process. While perl itself laudably sets the close-on-exec flags on new
802	file handles, most C libraries don't care, and even if all cared, it's	1018	file handles, most C libraries don't care, and even if all cared, it's
803	often not possible to set the flag in a race-free manner.	1019	often not possible to set the flag in a race-free manner.
…		…
823	libraries or the code that leaks those file descriptors.	1039	libraries or the code that leaks those file descriptors.
824		1040
825	Fortunately, most of these leaked descriptors do no harm, other than	1041	Fortunately, most of these leaked descriptors do no harm, other than
826	sitting on some resources.	1042	sitting on some resources.
827		1043
828	=item "leaked" file descriptors for fork'ed processes	1044	=item leaked file descriptors for fork'ed processes
829		1045
830	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,	1046	Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
831	which closes file descriptors not marked for being inherited.	1047	which closes file descriptors not marked for being inherited.
832		1048
833	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer	1049	However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
…		…
842		1058
843	The solution is to either not load these modules before use'ing	1059	The solution is to either not load these modules before use'ing
844	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay	1060	L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
845	initialising them, for example, by calling C<init Gtk2> manually.	1061	initialising them, for example, by calling C<init Gtk2> manually.
846		1062
847	=item exit runs destructors	1063	=item exiting calls object destructors
848		1064
849	This only applies to users of Lc<AnyEvent::Fork:Early> and	1065	This only applies to users of L<AnyEvent::Fork:Early> and
850	L<AnyEvent::Fork::Template>.	1066	L<AnyEvent::Fork::Template>, or when initialising code creates objects
		1067	that reference external resources.
851		1068
852	When a process created by AnyEvent::Fork exits, it might do so by calling	1069	When a process created by AnyEvent::Fork exits, it might do so by calling
853	exit, or simply letting perl reach the end of the program. At which point	1070	exit, or simply letting perl reach the end of the program. At which point
854	Perl runs all destructors.	1071	Perl runs all destructors.
855		1072
…		…
874	to make it so, mostly due to the bloody broken perl that nobody seems to	1091	to make it so, mostly due to the bloody broken perl that nobody seems to
875	care about. The fork emulation is a bad joke - I have yet to see something	1092	care about. The fork emulation is a bad joke - I have yet to see something
876	useful that you can do with it without running into memory corruption	1093	useful that you can do with it without running into memory corruption
877	issues or other braindamage. Hrrrr.	1094	issues or other braindamage. Hrrrr.
878		1095
879	Cygwin perl is not supported at the moment, as it should implement fd	1096	Since fork is endlessly broken on win32 perls (it doesn't even remotely
880	passing, but doesn't, and rolling my own is hard, as cygwin doesn't	1097	work within it's documented limits) and quite obviously it's not getting
881	support enough functionality to do it.	1098	improved any time soon, the best way to proceed on windows would be to
		1099	always use C<new_exec> and thus never rely on perl's fork "emulation".
		1100
		1101	Cygwin perl is not supported at the moment due to some hilarious
		1102	shortcomings of its API - see L<IO::FDPoll> for more details. If you never
		1103	use C<send_fh> and always use C<new_exec> to create processes, it should
		1104	work though.
		1105
		1106	=head1 USING AnyEvent::Fork IN SUBPROCESSES
		1107
		1108	AnyEvent::Fork itself cannot generally be used in subprocesses. As long as
		1109	only one process ever forks new processes, sharing the template processes
		1110	is possible (you could use a pipe as a lock by writing a byte into it to
		1111	unlock, and reading the byte to lock for example)
		1112
		1113	To make concurrent calls possible after fork, you should get rid of the
		1114	template and early fork processes. AnyEvent::Fork will create a new
		1115	template process as needed.
		1116
		1117	undef $AnyEvent::Fork::EARLY;
		1118	undef $AnyEvent::Fork::TEMPLATE;
		1119
		1120	It doesn't matter whether you get rid of them in the parent or child after
		1121	a fork.
882		1122
883	=head1 SEE ALSO	1123	=head1 SEE ALSO
884		1124
885	L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),	1125	L<AnyEvent::Fork::Early>, to avoid executing a perl interpreter at all
		1126	(part of this distribution).
		1127
886	L<AnyEvent::Fork::Template> (to create a process by forking the main	1128	L<AnyEvent::Fork::Template>, to create a process by forking the main
887	program at a convenient time).	1129	program at a convenient time (part of this distribution).
888		1130
889	=head1 AUTHOR	1131	L<AnyEvent::Fork::Remote>, for another way to create processes that is
		1132	mostly compatible to this module and modules building on top of it, but
		1133	works better with remote processes.
		1134
		1135	L<AnyEvent::Fork::RPC>, for simple RPC to child processes (on CPAN).
		1136
		1137	L<AnyEvent::Fork::Pool>, for simple worker process pool (on CPAN).
		1138
		1139	=head1 AUTHOR AND CONTACT INFORMATION
890		1140
891	Marc Lehmann <schmorp@schmorp.de>	1141	Marc Lehmann <schmorp@schmorp.de>
892	http://home.schmorp.de/	1142	http://software.schmorp.de/pkg/AnyEvent-Fork
893		1143
894	=cut	1144	=cut
895		1145
896	1	1146	1
897		1147

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Comparing AnyEvent-Fork/Fork.pm (file contents): Revision 1.29 by root, Sat Apr 6 09:15:49 2013 UTC vs. Revision 1.66 by root, Sat Jun 20 13:24:54 2015 UTC

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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.29 by root, Sat Apr 6 09:15:49 2013 UTC vs.
Revision 1.66 by root, Sat Jun 20 13:24:54 2015 UTC